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Articles 1 - 5 of 5
Full-Text Articles in Structures and Materials
Finite Element Frequency Domain Solution Of Nonlinear Panel Flutter With Temperature Effects And Fatigue Life Analysis, David Yongxiang Xue
Finite Element Frequency Domain Solution Of Nonlinear Panel Flutter With Temperature Effects And Fatigue Life Analysis, David Yongxiang Xue
Mechanical & Aerospace Engineering Theses & Dissertations
A frequency domain solution method for nonlinear panel flutter with thermal effects using a consistent finite element formulation has been developed. The von Karman nonlinear strain-displacement relation is used to account for large deflections, the quasi-steady first-order piston theory is employed for aerodynamic loading and the quasi-steady thermal stress theory is applied for the thermal stresses with a given change of the temperature distribution, ΔΤ (x, y, z). The equation of motion under a combined thermal-aerodynamic loading can be mathematically separated into two equations and then solved in sequence: (1) thermal-aerodynamic postbuckling and (2) limit-cycle oscillation. The Newton-Raphson iteration technique …
Integrated System Identification And Adaptive State Estimation For Control Of Flexible Space Structures, Chung-Wen Chen
Integrated System Identification And Adaptive State Estimation For Control Of Flexible Space Structures, Chung-Wen Chen
Mechanical & Aerospace Engineering Theses & Dissertations
Accurate state information is crucial for control of flexible space structures in which the state feedback strategy is used. The performance of a state estimator relies on accurate knowledge about both the system and its disturbances, which are represented by system model and noise covariances respectively. For flexible space structures, due to their great flexibility, obtaining good models from ground testing is not possible. In addition, the characteristics of the systems in operation may vary due to temperature gradient, reorientation, and deterioration of material, etc. Moreover, the disturbances during operation are usually not known. Therefore, adaptive methods for system identification …
The Solution Of A Singular Integral Equation Arising From A Lifting Surface Theory For Rotating Blades, Mark H. Dunn
The Solution Of A Singular Integral Equation Arising From A Lifting Surface Theory For Rotating Blades, Mark H. Dunn
Mathematics & Statistics Theses & Dissertations
A technique is presented for the solution of a linear, two dimensional, singular, Volterra integral equation of the first kind. The integral equation, originally developed by Farassat and Myers, is derived from the basic equations of linearized acoustics and models the lifting force experienced by an infinitesimally thin surface moving tangent to itself. As a particular application, the motion of modern high speed aircraft propellers (Advanced Technology Propellers) is considered. The unknown propeller blade surface pressure distribution is approximated by a piecewise constant function and the integral equation is solved numerically by the method of collocation. Certain simplifying assumptions applied …
High Heat Flux Cooling For Spacecraft Electronics, Louis C. Chow, John E. Leland
High Heat Flux Cooling For Spacecraft Electronics, Louis C. Chow, John E. Leland
Office for Research Publications and Presentations
An experimental investigation of flow boiling in a curved channel has been performed to ascertain its value in electronics cooling applications. Results have been obtained for flow velocities of 1 to 5 m/s and subcooling of 0.5 to 40 K. These results were compared to those of straight channel under identical velocity and subcooling conditions. The critical heat flux of the curved channel was found to be greater than that of the straight channel. In some cases the increase was found to be marginal, however. An unexplained temperature shift in the nucleate boiling regime was experienced during some experiments. Because …
Radiometer For The Investigation Of Infrared Emissions From Flames And Rocket Plumes, Kathy Underhill, M. Keith Hudson, Jason Willis, Mokhtar Mofidi, Matthew J. Russo
Radiometer For The Investigation Of Infrared Emissions From Flames And Rocket Plumes, Kathy Underhill, M. Keith Hudson, Jason Willis, Mokhtar Mofidi, Matthew J. Russo
Journal of the Arkansas Academy of Science
A prototypical radiometer using standard one inch interference filters and a lead selenide detector was constructed for use in flame and rocket plume studies. This radiometer was designed to employ a 600 Hz chopper and chopper frequency/phase reference circuit for signal processing. Bandpass filters centered for either 2.7 mum or 4.45 mum were placed in the optical path. The passed carbon dioxide or water vapor band energy irradiated the lead selenide detector, resulting in an output voltage. This signal was then fed into a dedicated synchronous detector. The signal was then recorded by a computer system equipped with an analog-to-digital …